At present, gate lines, gate electrodes, source electrodes, drain electrodes and data lines of thin film transistor liquid crystal displays (TFT-LCD) are generally made of Ta, Cr, Mo and other metals or metal alloys formed from the above mentioned metals which have relatively stable chemical properties and relatively high resistivities. Because of a smaller size and a lower resolution of the TFT-LCD, the delay of the gate signal is relatively small, which has no obvious effect on the display effect of the TFT-LCD. With the increasing of the size and resolution of the TFT-LCD, the length of the gate line increases, and thus the signal delay time increases as well. In a case that the signal delay increases to a certain extent, some pixels may not be fully charged, which may cause uneven brightness, so that the contrast of the TFT-LCD is reduced and the display quality of the image is seriously affected. Therefore, a low resistance metal may be used to manufacture the gate lines, the gate electrodes, the source electrodes, the drain electrodes and the data lines of thin film transistor liquid crystal displays to solve the above mentioned problem.
In a case that the metal lines or metal electrodes made of a low resistance metal are under high temperature condition, low resistance metal ions are prone to diffuse into the semiconductor layer, and the performance of the thin film transistor is deteriorated, which seriously affects the performance of the TFT.